Method and device for shrouding a stream of metal teemed through a slidable gate

ABSTRACT

An extended tube nozzle construction in conjunction with a slidable gate for bottom pouring molten metal. Includes a telescoping shroud plate which rests on the receiving vessel when in the operating position.

United States Patent 1 Andrzejak et a1.

[ 1 July 31, 1973 METHOD AND DEVICE FOR SIIROUDING A {58] Field ofSearch [64/66, 136, 281, STREAM OF METAL TEEMED THROUGH A 164/337;222/512; 266/34 V, 38

SLIDABLE GATE I75 I Inventors: Sigmund L. Andrzejak, Chicago; [56]Raymond B. Berg, Calumet City, v UNITED STATES PATENTS both Of 1".1,417,269 5/1922 MacMichael et a1. 164/337 3,501,068 3/1970 Shapland222/512 [73] Assignee: United States Steel Corporation,

Pittsburgh, Pa. Primary Examiner-Gera1d A. Dost 221 Filed: Mar. 16, 1912[211 App]. No.: 235,387 [57 ABSTRACT Rehted s Application Data Anextended tube nozzle construction in conjunction [63] continuation ofSer. No 4 965 Jan 22 1970 with a slidable gate for bottom pouring moltenmetal. abandoned Includes a telescoping shroud plate which rests on thereceiving vessel when in the operating position,

[52] U.S. Cl 266/38, 164/136, 164/281, 2 Claims, 3 Drawing Figures [51]Int. Cl C211) 7/14 p I I lo I5 I I9 ,1: I'll I 20 27 29 22 ":2 if 2 28 EPATENIED JUL3 I I975 INVENTORS 8 RAYMOND B. BERG Alla/0g SIGMUND L.ANDRZEJAK METHOD AND DEVICE FOR SIIROUDING A STREAM OF METAL TEEMEDTHROUGH A SLIDABLE GATE This application is a continuation of Ser. No.4,965, filed Jan. 22, l970, and now abandoned.

This invention relates to an improvedmethod and device for shrouding astream of metal teemed through a slidable gate.

Although our invention is not thus limited, the apparatus isparticularly advantageous as applied to a continuous-casting operationfor steel. Oxides of iron and of deoxidizers added to the steel in thefurnace or the ladle form as the molten steel is teemed through air intoa receiving vessel, such as a continuouscasting mold. These oxides, suchas iron oxide, alumina and silica, are insoluble in molten steel andform a slag-like layer which floats on the surface of the molten steelin the mold. The oxides collect near the mold walls and descend with thesteel casting along the surface thereof. As the casting surfacesolidifies, the oxides solidify on or near the casting surface. Theoxides impair the quality of the surface and must be removed by suitabletreatment such as scarfing.

Exposure of the molten steel stream to air during teeming also resultsin surface cracks, pits, scabs and ripples due to the turbulence of thesteel stream caused by entrainment of air.

In order to minimize oxidation of steel as it is teemed and to minimizesurface irregularities due to a turbulent steel stream, it is known toprotect the stream from exposure to air during teeming. This is commonlyaccomplished by providing an enclosed passageway in the form of a tubefor the pouring stream, which tube extends downwardly from ,the teemingvessel into the mold. However, when such tube is used in combinationwith a slidable gate mechanism, the tube must be positioned beforehandand the gate mustoperate above the tube. Thus itcan be seen that such atube must necessarily be affixed to the mold. This requires a complexmold-top design, and changing tubes during a cast is virtuallyimpossible. I i v It is an object of our invention to provide a slidablegate apparatus which'includes an enclosed passage for molten metal;

Another objectis to provide a simple inexpensive i method and means ofshrouding the pouring stream,

and molten metal in a mold when the pouring vessel is equipped with aslidable gate.

A further object of this invention is to provide a pouring device whichprotects molten metal from oxidation by air as the metal is teemed froma ladle through a slidable gate into a continuous-casting mold. v

Thetube of our invention is integral withand extends downwardly from aslidable gate and'moves into position over the mold cavity with thegate. The tube carries a telescoping shroud plate which, when released,slides down the fixed tube into the operative position against the moldcover.

In the drawings:

FIG. I is a vertical sectional view of portions of a bottom-pour vesseland a receiving vessel, showing our improved protective device.

FIG. 2 is a horizontal section taken along line IIII of FIG. 1.

FIG. 3 is an alternative embodiment in which the protective deviceextends into the receiving vessel.

FIG. 1 shows portions of a conventional bottom-pour vessel 10 andreceiving vessel I2,both of which are refractory lined forcontainingmolten metal. In the example of a continuous-castingoperation, vessel 12 is a mold which oscillates vertically, as known inthe art. The bottom wall of the bottom-pour vessel has an outlet opening14 and carries a refractory discharge nozzle 15 fixed to its undersidealigned with the opening. Also as known in the art, a series of slidablegates 16 is mounted beneath the nozzle. The gates can be supported andoperated in any desired manner; hence we have not shown the supportingand operating mechanism. In accordance with our invention, each gatecomprises an extended refractory tube 18 surrounded by a refractoryinsert 19 and a steel frame 20. Slidablydisposed on tube 18 is a shroudplate 22 which comprises an impact-resistant refractory insert 23, asteel frame 24 surrounding the insert, and a graphite lubricating ring25. Tube 18 can be covered by a steel sleeve (not shown) if desired.Tubes of varying lengths may be provided for successive gates, as thetube is of fixed length. Eyelets 27 and 28 are affixed to the upper andlower frames respectively. Before the gate is aligned with the nozzle,shroud plate 22 is held in the upper or standby position by a hook orwire 29 which fastens eyelet 28 to. eyelet 27 as shown at the right ofFIG. 1. When the hook is unlatched or the wire is cut, shroud plate 22slides down tube 18 into operating position atop mold cover l2, as shownat the left of FIG. I. The resulting impact requires that the refractoryinsert 23 be a highly fracture-resistant material. The graphitelubricating ring 25 provides lubrication as the shroud plate 22oscillates with the mold. Both gate '16 and shroud plate 22 aredisposable, as they are simple low cost items. Shroud plate 22 hasa viewport 31' of a heat-resistant transparentmaterial and an opening 32 topermit the introduction of an inert gas to the top of the mold.

FIG. 3 depicts an alternative embodiment wherein'a shroud plate 35 ispermanently affixed to alower refractory tube 36 which is slidablydisposed'on' upper tube 37. The lower tube may extend into the receivingvessel 38 as far as desired, limited only by the distance required bythe tube to clear the receiving vessel when in the upper or standbyposition. 1 I 1 The additional tube extension beneath the top of themold reducesturbulence in the mold, thus helping to prevent breakouts.When changing an active gate having a tube which extends into the mold,the telescoping portion isfirst raised manually by lifting eyelet 39.When the shroud plate is in' the operative positiona'top the mold and aninert gas such as argon" is 'being'introduced through opening 32,substantially all atmospheric oxygen is excluded from the molten steel.

From the foregoing description it is seen that our invention affords asimple effective construction for maintaining an enclosed passagebetween a bottompour vessel and a receiving vessel. Since all parts areintegral with a slidable gate, the receiving vessel need not be of aspecial design. Further, if any difficulty arises during teeming, adefective extended tube gate can be easily replaced by a new gate orteeming can be interrupted by use of a regular closure gate.

We claim:

1. In combination, a bottom-pour vessel having an outlet in its bottomwall, a receiving vessel which oscillates vertically and has an openingin its top beneath said bottom-pour vessel and an apparatus for teemingsel, and releasable means which connects said plate to said gate andsupports said shroud plate in said raised position on said tube. I

2. An improvement as defined in claim I in which said shroud-platecomprises a metal frame, an impact resistant refractory insert in saidframe, said insert having a substantially vertical hole therethrough, agraphtube with said outlet and said opening, and a lowered position inwhich it engages the top of, covers the opening of and oscillatesvertically with said receiving vesite lubricating ring fixed in saidhole, and means attached to said frame for engaging said releasable t it i f

1. In combination, a bottom-pour vessel having an outlet in its bottomwall, a receiving vessel which oscillates vertically and has an openingin its top beneath said bottom-pour vessel and an apparatus for teemingmetal from said bottom-pour vessel into said receiving vessel, saidapparatus including a slide-through gate slidably attached to theunderside of said bottom-pour vessel and a refractory pouring tubedepending from said gate and adapted to be aligned with said outlet andsaid opening, a shroud plate slidably mounted on said tube having araised position adjacent said gate, which position said plate occupiesprior to alignment of said tube with said outlet and said opening, and alowered position in which it engages the top of, Covers the opening ofand oscillates vertically with said receiving vessel, and releasablemeans which connects said plate to said gate and supports said shroudplate in said raised position on said tube.
 2. An improvement as definedin claim 1 in which said shroud plate comprises a metal frame, an impactresistant refractory insert in said frame, said insert having asubstantially vertical hole therethrough, a graphite lubricating ringfixed in said hole, and means attached to said frame for engaging saidreleasable means.